The purpose of this study is to monitor safety and measure changes in ureagenesis resulting from gene therapy in patients with ornithine transcarbamylase deficiency (OTCD). OTCD is an inborn error of urea synthesis inherited as an X-linked disorder. Classically, affected males present with hyperammonemic coma in the newborn period while heterozygous females have a spectrum of clinical presentations, ranging from asymptomatic to severe symptoms. Current treatment relies on alternate pathway therapy or liver transplantation, and the outcome remains bleak. A Phase I study of adenoviral mediated gene therapy is being carried out at the University of Pennsylvania on adult heterozygotes with this disorder. We are a collaborating institution in this study and plan 1)to perform heavy isotope (15N)/allopurinol studies to measure effecacy of the experimental treatment in correcting deficits in urea synthesis; and 2) to obtain blood for liver, renal, hematologic, and immune function to study safety in subjects with OTC deficiency.